Hull Repairs

Discussion in 'Fiberglass and Composite Boat Building' started by majorm, Feb 10, 2013.

  1. majorm
    Joined: Apr 2012
    Posts: 18
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    Location: South Carolina, USA

    majorm Junior Member

    We have had a project boat sitting around for maybe 10 years and I want to do something with it. The hull is very dry now and has a good bit of cracking and issues below the waterline. Above the waterline it looks good other than needing new paint. What would be the correct way to repair this? I thought about soda or abrasive blasting but dont know how that will turn out. The other option I thought of was a gelcoat peeler but Ive never used one or will have a use for one after the project. Take note that this isnt limited to just these areas.


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  2. Eric Sponberg
    Joined: Dec 2001
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    Location: On board Corroboree

    Eric Sponberg Senior Member

    Soda blasting will be good for a lot of areas, particularly around the hard corners. Gel coat peelers would be good for the broader and flatter areas. You can set the depth of a gelcoat peeler really fine and take off only a few thousandths at a time so that you are careful not to go too deep into the laminate. And there is always soft pad grinders which can take down gelcoat pretty quickly, not to mention hand sanding. I'd recommend the soft-pad grinders first, then also soda blasting and hand sanding, and that will get you most of the way, if not all the way, before having to consider a gelcoat peeler.

    Eric
     
  3. majorm
    Joined: Apr 2012
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    Location: South Carolina, USA

    majorm Junior Member

    Thanks for the quick reply. Ill try the soft pad on the grinder and see how that goes. I have a smaller air angle grinder that would work good for the small areas but even with ear plugs I dont know that I could stand it for as long as its going to take. I have a larger electric one I can use on the larger portions. Do you have any suggestions for grit since ill need to get those pads for the electric grinder? I wish dry Ice blasting wasnt so expensive. Id really like to give that a try and could do the engines at the same time. Media that evaporates seems much better than something that could stay embedded in the fiberglass.
     
  4. Eric Sponberg
    Joined: Dec 2001
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    Location: On board Corroboree

    Eric Sponberg Senior Member

    You want to start off with a coarse grit of 40 or 60, and work your way down to about 100 to 150. The gelcoat will be on the order of 0.025" to 0.030", about the thickness of a matchbook cover. The coarser grit will get you down almost all the way down to bare fiberglass--you'll see it showing in small areas. When you get that far, switch to a finer grit to take off the rest but not so much that you take off too much of the fiberglass and resin right underneath. What remains should be sufficient preparation for priming and painting.

    Eric
     
  5. tazmann
    Joined: Aug 2005
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    Location: California

    tazmann Senior Member

    I guess I will chime in here sense I stripped off gel coat and outer layer of mat with grinders, the grinders spin fast so you need to stick with the coarse grit around 40 to 60, the finer grits get to hot and smear the surface. when the surface gets down close to where you want is switch to a dual action, I used an air one but you do need a good sized CFM compressor to run one. I stayed with the 40 grit on the DA sander to leave a good tooth for the epoxy to stick to.
    Nasty dirty job, wear a good respirator and douse your body with baby powder before starting, helps keep the itching away
    Tom
     

  6. Steve W
    Joined: Jul 2004
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    Location: Duluth, Minnesota

    Steve W Senior Member

    I have an old Lindenberg 26 project boat that looks exactly the same , the gelcoat and at least the first layers of mat need to come off, for this i was going to build a gelcoat peeler but actually found a Gelplane for a reasonable price on ebay so i hope to find the time to peel it next summer. The boat is very dry, no meter reading at all. I have used grinders for this in the past as well as sandblasting and wont go that route again, it is a miserable job. Years ago a friend had to remove the first layers of mat from the sheerline down to the waterline on a 40ft J boat and then relaminate fair and awlgrip, a big job which he came up with a rather clever solution, he didnt dick around with soft pads on a sander/polisher, he built a dust shroud out of fiberglass for a big milwaukee grinder, he used a foam seal around the bottom of the shroud and drilled holes in it so he could tape over them so that when he had it hooked up to the vacuum he could adjust it so it supported the weight of the rather heavy but powerful grinder so he just had to move it around, he used 8" 16 grit Zek discs and it worked brilliantly.
    There is a tool called the "Marine shaver pro" which is another modified angle grinder which i had considered which may work for your boat, i didnt think it would work well on a round sailboat hull but there is a video of it in action on a hard chine powerboat bottom and it looks good, they are not too expensive, about 1/3rd the price of a Gelplane new but as they are sold more often for stripping siding on houses under the name of "paint shaver pro" you can always find them used on ebay, it seems people shell out a grand for the tool, strip their house and then sell them on ebay and recoup 2/3rd of the price, not a bad idea really, the compaany is american and also rents them so that may be a good way to go also, you actually have to buy it up front and then when you return it the charge you for the days you used it and refund the balance. Food for thought.

    Steve.
     
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